Lab talk

Researchers at Texas Tech University, US, are studying the integration of nanocrystals into polymer solar cells. The combination is a potential substitute for traditional silicon photovoltaics with benefits such as low-cost assembly and a flexible form factor, but there are technical issues to overcome. Bulk heterojunction polymer solar cells, consisting of an interpenetrating network of conjugated polymer and fullerene derivative, have shown low carrier mobility and open circuit voltage. Shiren Wang's group is employing semiconducting carbon nanotubes to solve these problems.

The researchers prepare their devices by creatively conjugating poly (3-hexylthiophene)(P3HT) onto carbon nanotubes by π-π interactions and avoiding chemical modifications. Through photoluminescence characterization and carrier mobility measurements, the role of semiconducting carbon nanotubes in the photovoltaic conversion is revealed.

A filtration process is used to tailor the purity of semiconducting carbon nanotubes and adjust the dispersion morphology of the material in the conjugated composites. Further thermal annealing helps to improve the structure of nanotube/P3HT composites and forms a type-II heterojunction. As a result, both short-circuit current and open-circuit voltage are significantly enhanced, and the power conversion efficiency is increased by 80%.

The techniques outlined in the study can be extended to other organic photovoltaic systems, and may pave a way to affordable and efficient solar cells.

About the author

Prof. Shiren Wang is leading a group investigating the synthesis and characterization of well defined nanostructures, as well as nanomaterials-enhanced energy conversion and storage. He is a recipient of National Science Foundation CAREER and 3M young faculty awards.